Percentage Calculator
Work out a percentage of a number, what percent one number is of another, the percentage change between two values, or a number raised or lowered by a percentage. Results update as you type, with the working shown.
What is X% of Y?
Result
Enter both numbers to see the result.
X is what percent of Y?
Result
Enter both numbers to see the result.
X is Y% of what number?
Result
Enter both numbers to see the result.
Percentage change from X to Y
Result
Enter both numbers to see the result.
Increase or decrease X by Y%
Result
Enter both numbers to see the result.
The calculation runs in this browser tab. Nothing you enter is uploaded, saved or logged.
What is a percentage?
A percentage is a number written as a part of 100. The word comes from the Latin per centum, “by the hundred”, so 25% means 25 out of every 100, which is 0.25 as a decimal or 1/4 as a fraction.
Percentages are used to describe a share of a whole (a 15% tip, 8% sales tax), to compare two quantities (this month’s sales are 120% of last month’s) and to describe a change (prices rose by 4%). A percentage only means something next to the amount it is measured against, so each question on this page names that base: a percentage “of” a number, a number “of” another number, or a change “from” a starting value.
How to use the Percentage Calculator
- Pick the question that matches your problem. Each of the five calculators above answers one question.
- Type the two numbers in the labelled fields. Use a dot for decimals (12.5), a minus sign for negative numbers, and no thousands separators.
- The result and the working appear as you type. If you need a fixed number of decimals, choose it in the “Round to” menu.
- Use Copy result to copy that answer, or Reset to clear all five calculators.
Formula
- Percentage of a number
- result = (percentage ÷ 100) × number
- What percent one number is of another
- percent = (part ÷ whole) × 100
- Finding the whole from a part
- whole = part ÷ (percentage ÷ 100)
- Percentage change
- change % = (new − old) ÷ |old| × 100
- Increase or decrease by a percentage
- result = number × (1 ± percentage ÷ 100)
|old| is the absolute value of the starting number. Dividing by it means a positive change is always an increase, even when the starting value is negative. A change from 0 has no percentage, so the calculator reports that instead of a number.
Percent and percentage points are different. Going from 10% to 12% is a rise of 2 percentage points, but a 20% increase in the rate itself.
Worked example
A jacket costs 240 and is 15% off. Later, a different item goes from 200 to 250. These are the results the calculator gives for those numbers:
| Question | Result |
|---|---|
| What is 15% of 240? | 36 |
| 240 decreased by 15% (the sale price) | 204 |
| 36 is what percent of 240? | 15% |
| 36 is 15% of what number? | 240 |
| Percentage change from 200 to 250 | 25% |
Assumptions and limits
- Numbers you type are read as exact decimals and the arithmetic is done on whole numbers, so floating-point noise such as 0.07 × 100 = 7.000000000000001 never appears in a result.
- If an exact answer has more than 10 decimals (1 ÷ 3, for example), it is rounded to 6 decimals (more for very small values, so a non-zero result never shows as 0) and marked with ≈. Choose a number of decimals in “Round to” to override this. Rounding is half away from zero: 2.5 becomes 3 and −2.5 becomes −3.
- Inputs can have up to 30 digits. A decimal comma is not accepted: “1,234” means 1234 in some countries and 1.234 in others, so the calculator asks you to type 1234 or 1.234 rather than guess.
- The tool does pure arithmetic. For tax, pricing or legal work, check how the rules that apply to you round and order their calculations.
Frequently asked questions
How do I calculate a percentage of a number?
Divide the percentage by 100 and multiply by the number. For 15% of 240: 15 ÷ 100 = 0.15, and 0.15 × 240 = 36.
How do I calculate percentage increase or decrease?
Subtract the old value from the new value, divide by the old value, and multiply by 100. From 200 to 250: (250 − 200) ÷ 200 = 0.25, so the increase is 25%. A negative result means a decrease.
Why doesn’t a 50% increase followed by a 50% decrease get me back to the start?
The second percentage applies to a different base. 100 up by 50% is 150, and 50% of 150 is 75, so you end at 75. To undo a 50% increase you need a decrease of 33.33…%, because 50 is one third of 150.
What is the difference between percent and percentage points?
A percentage point is a plain difference between two percentages. If an interest rate moves from 4% to 5%, it rises by 1 percentage point, which is a 25% increase relative to the old rate.
Can a percentage be more than 100 or negative?
Yes. 150% of 80 is 120, because 150% means one and a half times the number. A negative percentage gives a negative share: −10% of 50 is −5. Decreasing a number by more than 100% takes it below zero, and the calculator shows that as is.
How is the result rounded?
If the exact answer has at most 10 decimals it is shown in full. Otherwise it is rounded to 6 decimals (more for very small values) and marked as approximate. You can choose 0 to 6 fixed decimals instead; the calculator then rounds half away from zero.